Every year, an estimated 11,000 to 14,000 children in the United States are hospitalized due to heart failure, however the mechanisms which underlie the development of heart failure in infants remain to be fully understood. It is known that after birth increased oxygen levels and changing substrate availability drive cardiomyocytes to switch from relying on glycolysis for energy production to primarily utilizing fatty acid oxidation. While it was previously believed that mitochondria are flexible in their substrate usage, it is now known that mitochondrial turnover is necessary to drive metabolic reprogramming and that mitophagy is critical to the process of mitochondrial clearance. However, it is not known whether the breakdown of metabolic reprogramming contributes to the development of neonatal heart failure. The long-term goal of this project is to prevent the development of heart failure in infants. Having previously identified GRAF1 as a striated muscle- selective focal adhesion kinase (FAK) binding partner that is expressed at high levels in the heart from late embryogenesis onward, our current data indicate that GRAF1 plays an important role in regulating cardiac mitochondrial clearance and metabolism. Mitochondria are particularly abundant in cardiomyocytes and the dependence of these long-lived cells on oxidative phosphorylation-mediated ATP generation for contraction necessitates turnover and replacement of mitochondria every 2-3 weeks in un-stressed hearts. Mitochondria produce reactive oxygen species (ROS) as a byproduct through leakage of electrons from the electron transport chain and even slight dysfunctions can disrupt the redox balance which further perpetuates mitochondrial dysfunction and cell death. The fact that the pathological progression of disease is markedly accelerated by lack in mitochondrial quality control highlights the importance of discovering the underlying mechanisms. This study?s objective is to implicate GRAF1-dependent metabolic reprogramming as a novel therapeutic target for pediatric heart failure. My central hypothesis is that the Rho-GAP GRAF1 is a novel autophagy receptor and that its inhibition will disrupt the clearance of ROS-producing mitochondria and will attenuate the promotion of neonatal metabolic reprogramming thereby leading to heart failure in a perinatal murine model. The rationale for this study is that if the breakdown of metabolic reprogramming is found to be a part of the pathogenesis of pediatric heart failure, then it will represent a new avenue for the development of therapeutic agents. My aims for this award are two-fold: In aim1, we will undertake a step-wise approach to identify the precise mechanisms by which GRAF1 regulates the clearance of damaged cardiomyocyte mitochondria. In aim 2, we will use our newly developed cardiac-restricted GRAF1 knock-out mice to assess GRAF1?s contributions to mitochondrial clearance-dependent cardiac metabolic reprogramming. Results from the experiments proposed herein will provide the scientific foundation for the rational design of strategies to control cardiomyocyte mitophagy and could lead to novel approaches to treat perinatal heart disease.